Automatic control system for hoisting apparatus



J. E. AULD Jan. RO, H56

AUTOMATIC CONTROL SYSTEM FOR HOISTING APPARATUS Filed April 15, 1952 HHHHIHHH Huth INI EN TOR. (Jh/w55 E. Hun.

United States Patent AUTOMATIC CONTROL SYSTEM Y APPARATUS FOR HOISTIN G This invention relates generally to automatic control systems for hoisting apparatus suchas'craues, power shovels and the like. More particularly the invention relates to automatic control systems for stopping all fmotion of a hoisting apparatus when it approaches the safel limits of proximity to overhead power distribution lines voroth'er exposed sources of electrical energy.

Hoisting apparatus, such as cranes, power shovels and the like, is equipped with a hoistingV boom of appreciable length; and while the operators'of such hoistingapparatus develop a high degree ,of skill in controlling the motion of the boom, it frequently happens thatthe boom orthe cable carried by the boom' may accidently .come in contact with sources of electrical energy such as high voltage power distribution lines. Of course when such contact occurs, there is a direct electricalconnection to ground, and the resulting short circuit ,maycause ydestruction of the crane, injury or death to the operator and a serious disruption of electrical service. Incase ofextremely high voltage power lines it may not be necessary ,that theboom or the cable of the hoisting apparatus come into actual physical contact with the conductors of the power line. If the voltage is sufficiently high, an arc may form before the boom or cable actually contacts the power line, and such a phenomenon can cause an equally great amount of damage.

Accordingly, it is the principal object of this invention to provide an automatic control system for hoisting apparatus, such as cranes, power shovels and the like, which is adapted to stop all motion of the hoisting apparatus when and if such apparatus approaches a high voltage source of electrical energy within predetermined limits of proximity.

Another object of this invention is to provide an automatic control system for hoisting apparatus, such as cranes, power shovels and the like, which is operative to stop the driving motor of a hoisting apparatus, apply brakes to the cable winding drum and also to apply brakes to the gears which apply turning motion to the hoisting apparatus.

Still another object of this invention is to provide an automatic control system for hoisting apparatus such as cranes, power shovels and the like, which includes an automatically energized control circuit, which is responsive to closing of the driving motor ignition circuit.

In accordance with this invention there is provided an automatic control system for power hoisting apparatus comprising an antenna means responsive to an electromagnetic field such as that created in the vicinity of a power distribution line, an amplifier and master control relay responsive to signals generated by the antenna means, and means responsive to the master control relay for disabling the drive motor of the power hoisting apparatus and for applying brakes to the cable winding drum and turning mechanism of the hoisting apparatus.

The single figure of the drawings is a circuit diagram of the automatic control system provided in accordance with this invention.

' close when antenna 10 "of electrical energy,

lThis energy may be 'the secondary In accordance with this invention there is provided an automatic control system for hoisting apparatus, such as cranes, power shovels and the like, which include a boom for hoisting either various objects such as structural steel or various types of excavating apparatus. vReferring to the drawing there is provided an antenna 10 which may be mounted at the upper extremity of the hoisting boom 11 of a conventional crane or power shovel 12. Antenna 10 may be any form of conventional antenna. Coupled to the antenna 1t) is a conventional antenna circuit consisting of a condenser 14, a potentiometer 15 and a grounded resistor 16.

An amplifier circuit consisting of a first stageV 20 is coupled to the antenna circuit between condenser 14 vand potentiometer 1S. The output of amplifier stage 20 consists of a conventional audio transformer 21'across the primary of which is connected aihigh frequency bypass condenser 22. A second high frequency bypass condenser 23 may be connected across the secondary of transformer 21. The input of a second amplifier stage 25 may be connected across the secondary winding of transformer 2l, and the output of stage 25 may consist of a second audio transformer 26 having connected in the primary circuit thereof a high frequency bypass condenser 27. Amplfier stages 20 and 25 are conventional in every respect and serve to amplify signals 'occurring Vin,the circuit of antenna 16 when the boom 11 moves within, for example, l5 feet of a high voltage powerdistiibution line or other high voltagesource of electrical energy. It is well known that a magnetic field always exists around such sources and hence,' the antenna 10 in moving will pick up usable electrical energy. amplified in'stages 20 Vand 25 to prothrough suchl a field duce a usable signal.

vFor. utilizing this signal, `thereis provided a full wave vrectifier 28, the anodes of which are -,connected across of transformer 26. Secondary 26 is center tapped and connected to ground, and also connected to one side of the cathode of tube 28 through a condenser 30 and a resistor 31. The rectified energy put out by tube 28 is fed into the input of a trigger tube 33. Tube 33 is normally biased negatively by the grid biasing battery 34 and resistor 35 to such an extent that no signal appears in the anode circuit. However, when the antenna 10 enters an electromagnetic eld of predetermined strength, the output of rectifier 28 becomes sufficiently positive to bias on the control grid of tube signal appears in the anode circuit of tube 33. This signal is utilized by a master control relay 37 having a bypas condenser 38 shunted across its winding for bypassing alternating currents. The master control relay includes normally open contacts 39, which enters an electromagnetic field of predetermined strength to accomplish an automatic control function as will be described subsequently.

The hoisting apparatus 12 normally includes either a gasoline powered engine or a diesel engine, or in some cases a steam engine. In the case of a gasoline engine there is provided an ignition circuit including an ignition switch it? adapted to close a direct current circuit through the contact of a drop out relay 41, an ignition coil 42, a distributor and spar plugs (not shown) and battery 43. The winding of relay 41 may be connected between contacts 39 and battery 43 as shown. In the case of a diesel or steam engine, a valve in the fuel line may be provided for controlling the speed of operation of the engine. In such a case a fuel cutoff solenoid 44 may be connected between contacts 39 of master control relay 37 and battery 43, as will be described subsequently. For stopping the cable drum and the turning mechanism of a hoisting apparatus, conventional brakes may be incorporated in these mechanisms, and a solenoid (not shown) may be provided for applying the brakes when master control relay 37 operates. For controlling this solenoid a secondary control relay 46 may be connected to contacts 39 of relay 37 and to the battery 43, which is normally a component part of a gasoline or diesel power plant.

For automatically energizing the amplifier and its associated apparatus when the hoisting apparatus is operated, there may be provided a gang switch 43 having a switch arm 49 for closing the cathode circuits of tubes 20, 25 and 33. Switch 49 may also include a switch arm 50 for simultaneously closing the cathode circuit of tube 28. As already described, switch arm 40 is arranged to close the ignition system of the engine. v

When the antenna of the crane approaches a high voltage source of electrical energy, such as an exposed power line, it intercepts the magnetic eld created by the conductors of the power line. By adjusting the potentiometer 15, the sensitivity of the antenna circuit may be changed according to the voltage of the power line, and the minimum distance within which antenna 10 may approach the power line may be predetermined. Thus, when this minimum distance is attained, the magnitude of signal generated by tube 28 will be sufficient to operate the trigger tube 33 and produce a signal of suicient magnitude to energize relay 37, closing its contacts 39. It will thus be seen that the amplied signal in the output of tube 25 is fed to the anodes of tube 28 and therefore rectied, showing up across resistor 31 as a direct current and changing the bias of tube 33 to one of positive charge, allowing the plate current, supplied by the B battery, to tlow and actuate the relay. Upon such closure, relays 41 and 46 are energized to simultaneously open the ignition circuit of the crane engine and apply the brakes to the cable drum and turning apparatus. If the engine happens to be a diesel or steam engine, then solenoid 44 functions to cut off the supply of fuel or steam, thereby to stop the engine. Thus, it will be seen that there is provided, in accordance with this invention, an automatic control system for hoisting apparatus which will prevent the boom from coming into dangerous proximity to a source of high voltage electrical energy.

If it is so desired, the system may include a restoration switch 47 which normally may be locked in closed position so that, after the hoisting apparatus has been disabled by the control system, the foreman in charge of the apparatus may unlock the switch and proceed with reactivation of the apparatus.

The invention claimed is:

ln combination, a hoisting apparatus including a motivating system for said apparatus to prevent approach to a high voltage power line within predetermined limits of proximity, comprising an antenna mounted on the hoisting apparatus, an amplier including a filament cathode tube coupled to said antenna for deriving a useful signal when the antenna penetrates a magnetic field of predetermined intensity means for energizing said tube comprising a source of potential and a gang switch having contacts coupled to said source of potential and the filament cathode of said tube and contacts coupled to the motivating system of the hoisting apparatus for starting said apparatus, whereby said amplier is substantially instantaneously energized and operative when said hoisting apparatus is started, triggering means responsive to said signal when said antenna penetrates said magnetic eld, a master control relay operative in response to actuation of said triggering means to operate its contacts, and circuit means connected to the contacts of said relay and in operative relationship to said motivating system for stopping said hoisting apparatus when said master relay closes.

References Cited in the tile of this patent UNITED STATES PATENTS 1,973,414 Miller Sept. 11, 1934 2,529,193 Rueter Nov. 7, 1950 2,615,969 Albrecht Oct. 28, 1952 2,646,559 Nutzler July 21, 1953 

